In a process of manufacturing optic cables, a bundle of wholly aromatic polyamide filaments, which is formed by assembling multiple wholly aromatic polyamide filaments together, is generally used as a reinforcement material to cover optic fibers.
In order to increase surface area of an optic fiber and improve modulus thereof, a bundle of filaments, which is used to cover the optic fiber, is preferably maintained in a non-twisted state.
If the bundle of filaments is twisted, there are generally problems in that the modulus is lowered and a surface area of the bundle of filaments is decreased during the covering process of an optic fiber.
On the other hand, if the bundle of filaments has no twist, there is a problem occurring frequently in that some of the filaments in the bundle of filaments are partially loosened due to a deviation in tensions when a bundle of bundle of filaments is release-wound for post-processing such as the optic fiber covering process.
Consequently, for a process for manufacturing a bundle of filaments by assembling together multiple filaments, it is very important to endow a uniform tension to each of the filaments.
Among conventionally known processes for manufacturing a bundle of filaments, one is shown in FIG. 1. As shown in FIG. 1, a plurality of filaments are assembled together after being released from a creel part comprising separate creels which have bobbins 2 wound with the filaments, by using several driver rollers 3a, 3b and 3c and guide rollers 4a and 4b. Creels 1 fixed on rotational axes rotating by the axes under the release-winding tension. After passing the driver rollers 3a, 3b, 3c and guide rollers 4a and 4b, the bundle of filaments is wound around a winder 5 to produce a bundle of filaments. However, such process uses no device for regulating the release-winding tension of each of the filaments released from the bobbins, and therefore, has difficulty in controlling the release-winding tension of the filaments released from the creels to be constant.
The above process also has other problems that it is difficult to control the release-winding tension for each of the filaments released from the creels to be constant since the filaments released from the creels have different paths to a point for folding them and, especially, it is more difficult to control the tension to be constant in the cases when the filaments have higher deniers and when each of the filaments is irregularly wound around the creels.
FIG. 1 is a schematic view illustrating a conventional process for assembling multiple filaments into a bundle of the filaments.
The resulting bundle of filaments have an irregular or inhomogeneous distribution of weights of the filaments per unit length along the bundle of filaments and may be composed of filaments of different lengths, so that the filaments were partially hanging down due to lack of uniform tension when the bundle of filaments is released and wound during post-processing.
Furthermore, the bundle of filaments produced by a known process often suffers from a thread cutting when an optic fiber is covered by the bundle of filaments in manufacturing an optic cable thereby causing poor workability or an increase in production costs. More particularly, even when the bundle of filaments does not undergo thread cuttings, it is difficult to smoothly cover the optic fiber so that the optic cable manufactured using the bundle of filaments has disadvantages such as an uneven surface and reduced quality.
Meanwhile, in order to regulate the winding tension of a winder known in the related art, there was proposed a process for preventing a thread cutting by using a yarn feed roller that has a separate motor to control a rotational speed of the feed roller so as to maintain the winding tension of the winder constant. However, this process was only used for winding a single filaments under a constant winding tension, and thus, failed to manufacture a bundle of filaments without twisting by keeping a desired tension constantly applied to each of multiple filaments while assembling the filaments together.
Another known process for controlling a winding tension of a winder is to regulate the winding tension by mounting a magnetic brake on each of driving rollers so as to ease a difficulty in manufacturing a winding drum with a large dimension due to increased linear winding velocity depending on increased diameter of the winding drum. However, this process also has the same problem as the process for preventing a thread cutting with use of a yarn feed roller since a single filament only is wound under a uniform winding tension by the large winding drum. Therefore, it cannot keep a desired tension constantly applied to each of multiple filaments while folding together the filaments thereby being not able to manufacture a bundle of filaments in a non-twisted state.
If the filaments are release-wound or wound under non-uniform tension conditions, a variation in the filaments lengths occurs between individual filaments to be assembled. In cabling work of an optic cable by using such a bundle of filament, the bundle of filaments may be cut while passing through different guides and/or interfere with adjacent filaments which are release-wound when the bundle of filaments is release-wound while rotating in a cross winder, thereby possibly applying a heavy load to a machine used. Even without thread cuttings, the bundle of filaments has rough or uneven surface and a few strands in the form of loops pulled out of a surface of the filaments before coating the cable, thus, resulting in potentially significant irregular appearance during a coating process.
Furthermore, if there are thread cuttings, the bundle of filaments may be subjected to the cabling work with loss of at least one or more strands and/or may involve other problems such as reduced supporting force such as elasticity of an optic cable as a final product.